Bomb sight



Oct. 7, 1947. c. L. NORDE N El AL 2,428,673

BOMB SIGHT Filed May 27, 1930 ll Sheets-Sheet l Jiweziio'rs CARL L. NORDEN TuEODORE ".BARTH A TORNEY Oct. 7, 1947. c. NORDEN ET AL 2,423,678

BOMB SIGHT Filed May 27, 1930 11 Sheets-Sheet 2 ,Fwezaiors CARL L. NORDEN THEODORE HY BARTH HQLRQ M A ORN EY 1947- c. L. NORDEN ET AL 2,428,678

BOMB SIGHT Filed May 27, 1930 11 Sheets-Sheet 3 CARL \L NORDEN TEDDORE .BART

BY g. M M

ATTO NEY Oct. 7, 1947. c. L. NORDEN El AL 2,428,678

BOMB SIGHT Filed May 27, 1930 11 Sheets-Sheet 4 Oct. 7, 1947. c. L. NORDEN El AL 11 Sheets-Sheet 5 BOMB SIGHT Filed May 27, 1950 I-Illllll .fiwenlors CARLL NORDEN THEODORE n. sum

*MQL gym ATO RNEY Oct. 7, 1947.

C. L. NORDEN ET AL BOMB -SIGHT Filed May 27, 1930 ll Sheets-Sheet 6 m w I K s x m lllllslmlllmlmlliumu 1750491537: CARL L NORDEN THEDDORE wanna ORNEY Oct. 7, 1947. c. L. NORDEN ET AL 2,

' nous SIGHT Filed May 27, 1930 11 Sheets-Sheet 7 THEODORE H. BARTH TORNEY BYII u Oct. 7, 1947. c.- L. NORDVEN ET AL BOMB SIGHT Filed May 27, 1930 ll Sheets-Sheet 8 Iwezdbrs CARL L NORDEN THEODORE n. BARTH Oct. 7, 1947. c. NORDEN El AL 2,428,678

BOMB SIGHT Filed May 27, 1930 11 Sheets-Sheet 9 /.5'8 g f. p

.fiwaulors CARL L. NORDEN THEODORE H.BARTH AT ORNEY Oct. 7, 1947. c. L. NORDEN El AL BOMB SIGHT Filed May 27, 1930 11 Sheets-Sheet 10 a Lm mifovs CARL L NORD THEODORE H'BARTH Oct. 7, 1947. c. L. NORDEN ET AL 2,423,678

BOMB SIGHT ll Sheets-Sheet 11 Filed May 27, 1930 [27 jfiwl'zifirs CARL L. NORDEN THEODORE HBARTH mun Patented Oct. 7, 1947 BOMB SIGHT Carl L. Norden and Theodore H. Barth, New York, N. Y., assignors to United States of America, as represented by the Secretary of the Navy Application May 27, 1930, Serial No. 456,168

33 Claims.

Our invention relates broadly to an improvement in bomb sights and more particularly to a device that can be easily installed on an aircraft for the purpose of sighting and aligning a target at the proper angle to accurately drop a bomb from the air.

An object of our invention is to provide abomb sight wherein the optics are stabilized relative to the aircraft for the fore and aft position and for the athwartship position and the sight is stabilized about the vertical axis.

Another object of our invention is to provide in a bomb sight a stabilized optical system that can be moved without disturbing the stabilization thereof.

A further object of our invention is to provide with a bomb sight installed on an aircraft a mounting for the sight having apparatus thereon to indicate deflection and to allow overcorrection, thereby permitting steadier flying just before dropping the bomb.

Still a further object of our invention is to provide a bomb sight with a system of pilot directing wherein the bomb sight mounting and therefore the bomb sight is stabilized about the vertical axis. In this system, inasmuch as the sight optics are directly stabilized for the other two axes, the field picture should, when not on the collision course, show steady target drift unaffected by yawing of the aircraft or bumpy air.

With the above and other objects in view, our invention consists in the construction, combination and arrangement of parts as will be described more fully hereinafter.

Reference is to be had to the accompanying drawings forming a part of this specification, in which like reference characters indicate corresponding parts throughout the several views, and in which:

Fig. 1 is a diagrammatic view of the arrangement of our invention;

Fig. 2 is a sectional view of the optical system used in our improved device;

Fig. 3 is a plan view of the bomb sight in' our improved device with the top removed and partly shown in section;

Fig. 4 is a longitudinal section through the bomb sight of our improved device showing the gyro in elevation and the remaining parts in section;

Fig. 5 is a sectional view taken on line 5-5 of Fig. 4;

Fig. 6 is a sectional view taken on line 6-6 of Fig. 4;

2 Fig. '1 is a sectional view taken on line 1-1 of Fig. 4;

Fig. 8 is an end view of our improved bomb sight with a portion thereof removed;

Fig. 9 is an operating knob for the end of our improved bomb sight;

Fig. 10 is a plan view of the clock for our improved device with the face removed;

Fig. 11 is a central longitudinal section of the clock for our improved device;

Fig. 12 is a detail view of a portion of the clock for our improved device;

Fig. 13 is a longitudinal section through the pilot director of our improved device, shown part in elevation and part in section;

Fig. 14 is a detail sectional view of a, portion of the pilot director of our improved device;

Fig, 15 is a plan view of the pilot director of our improved device;

Fig. 16 is a side view of the pilot director of our improved device;

Fig. 1'7 is an end view of the bomb sight, shown partly in section, of our improved device;

Fig. 18 is a plan view of the pilot director bracket unit, showing a portion thereof in section. of our improved device;

Fig. 19 is a schematic arrangement of the pilot director and pilot director bracket unit of our improved device;

Fig. 20 is a wiring diagram for our invention:

Fig. 21 is a cross section of the clutch mechanism used in the bomb sight of our improved device;

Fig. 22 is a detail view partly in section of a portion of our invention.

Referring more particularly to the drawings, 20 indicates a sight casing consisting of an upper unit 2i and a lower unit 22 secured together by screws 23, and the end pieces 24 and 25. A circumferential groove 26 is machined at the center of the casing 20 to take a two-part ring collar 21 that is pivoted above the center line of the casing 20 by a fork 28 and pins 28, A cardan ring 30 is mounted longitudinally in the center of the casing 20 by ball bearings 3i carried on gudgeons 32 at each end of the casing 20. The fork pins or pivots 29 being above the center line of the sight makes the sight pendulic in the fork 28.

A gyro 33 is mounted in the left portion of the ring 30 by pins 34 and ball bearings 35. The gyro 33 has its cardan axis running fore and aft and at right angles to the axis of cardan 30. A rotor shaft 38 is mounted vertically in ball bearings 31 at the top and ball bearings 38 at the bottom of the gyro casing 33, and mounted on the shaft 39 are armature 39 and rotor 49. A field casing 4| secured to the bottom portion of gyro casing 33 has' field 42 and field pl e 43 x th r o y bolts 44 for operating the armature 39. The lower portion of the casing 33 is provided with a recess 45 for brushes 46 that bear against a commutator 41 secured adjacent the lower end of shaft 36. A cap 48 having a locking pin 49 extending therefrom closes the top of the casing 33.

Fore and aft bubble or level- 59 and athwartship bubble or level (Fig. 3) are positioned on the top of the casing 33 by clips 52 secured to the casing by screws 53. The clips 52 are provided with pointers 54 that extend over the center of the levels 59 and 5|. Also positioned on top of the casing 33 by means of screws 55 and clips 66 are threaded shafts 51 for an athwartship adjustable balance weight 58 and for a fore and aft adjustable balance weight 59.

Unit 2| of casing 29 has the apertured boss 69 in and around which 6|. The knob 6| when pushed down forces by means of hollow shaft 62 a cone 63 on the inside of the casing over the pin 49 on the cap 49 of the gyro casing. A pin 64 rojecting from shaft 62 rides in groove 65 in the boss 69 and when the knob 6| is pushed down and turned, pin 64 is adapted to rotate in a groove 66 thus locking the shaft and cone. from a locking position by the spring 91 when the knob BI is turned. When locking the gyro the locking knob 6| should be pressed down and turned anticlockwise. gyro to precess toward the central position, in which case the top of pin '49 will fit into the hol- -low of shaft 62 and lock the gyro.

A cradle 68 carrying an objective 69, a back eight 19 and their operating mechanism is mounted on the right side of the cardan 39 by means of sockets 1| secured with bolts 12 to the cardan 39 and cradle bearing pins 13 (Fig. 7) riding in the socket 1|. The tilting axis of the cradle is parallel to that of the gyro, and since the gyro and cradle are both mounted in the cardan they tilt together about the athwartship axis with the cardan. A rod 14 secured to a clip 15 attached by screws 16 to the cradle 68 and secured to clip 11 attached by screws 18 to the gyro 33, connects the gyro and cradle and insures that the gyro and cradle tilt together about their fore and aft axes. An objective mount 19 pivots in bearing 89 on each side of the cradle and can swing with the objective 69 through an angle.

The optical system as shown in Figure 2 consists of the tube or objective 69 and the eye piece In the objective 69 are mounted a cross line lens or reticle 82, a first objective lens doublet 63 and a second objective lens doublet 84. The eye piece has the erecting prism 85 and doublet eye piece lens 86. The objective is placed in the mount 19 and is stalized in the cradle while the eye piece is secured to unit 2| of the casing 29 and is not stabilized. The objective also has independent motion in the cradle 68, that is, it can be swung about the horizontal athwartship axis by manually operated mechanisms, while the plane of swing of the line of sight is held vertical by the gyro. The eye piece is lined up with the objective 69 by rotating the casing 29 in the fork 28 and by tilting the casing 29 about the fork pivots 29. Fore and aft line 81 and athwartship cross line 89 are engraved on the reticle 92 (Fig. 3).

The back sight 19 is simply a pointer secured by screws 89 to a shaft 99 rotatabiy placed on one of The cone 63 is quickly released is placed a gyro locking knob This will then cause the I the bearings 69 that acts as the axis for the mount 19 of the objective 69, but the back sight 19 turns independently of the objective mount 19. The pointer or back sight 19 extends one-half way across the field of the reticle 82 and is sufllcientiy clear of the objective 69 to allow independent motion of the back sight 19 and objective 69.

An operating cable 9| leads through the center of the after cradle bearing 13, and several turns are taken around a cable drum 92 which is keyed on an athwartship shaft 93 rotatably mounted on the sides of cradle 68. On one end of the shaft 93 outside of the cradle 68 is a. drum pinion 94 meshed with a large rack gear that is concentric with the objective mount axis. The large gear 95 meshes in racks 96 and 91 which slide in grooves 99 and 99, one at the top and one at the bottom of the cradle, respectively. The operating rack 91 carries a pin I 99 which projects through and slides in a slot |9| in guide lever I92 made fast to the objective mount 19 by a screw I93 so that motion of the rack 91 in the groove 99 swings the lever I92 and with it the-objective 69 through an arc in a fore and aft vertical plane. The top rack 96 moves in an opposite direction from the rack 91 and acts as a counter weight or balance to prevent the cradle 69 from being unbalanced due to movement of rack 91. A spiral spring I94 tends to turn the rack gear 95 connecting the racks 96 and 91 in a clockwise direction when viewed from the left. The tension on spring I94 opposes the pull on the operating cable 9|. A pull on cable 9| moves the objective 69 so that the line of sight approaches the vertical position. When the cable 9| is eased off, spring I94 moves the objective 69 in the opposite direction and winds up the slack cable on the drum 92.

Keyed on the right end of drum shaft 93 is a small gear I95 (see Fig. '7) that meshes with gear I96 turning idly on a clutch shaft I91 r0- tatably mounted through the right side of the cradle. Gear I96 has integral therewith a male clutch disk I98 (Fig. 21) and is held on to the shaft I91 by a cap I 99 on the end of the shaft so that when the clutch is disengaged, the gear I96, disk I96 and cap I99 turn idly on shaft I91 permitting the drum 92 to move independently. An electro magnet |I9 secured to the right side of the cradle by stud III (Fig. 3), arm 2 and stud H3 is energized by pressing a contact ring 4. The contact ring I I4 is secured to end plate 25 of the casing by spring I I5 and screws H6 and is positioned by positioning pin 1. When the electromagnet H9 is energized one end I I8 of a clutch operating lever H9 is drawn toward the magnet and the other end I29 bears against and pushes inward on cap I99. The cap I99 in turn forces the gear I96 and disk I98 to move into and become engaged with a female clutch disk I2I that is keyed to shaft I91. The lever I I9 is pivoted by pin I22 to a projecting end I23 of the arm II2. A spring -I-24 positioned around shaft I 91 between clutch disks I98 and I2| pushes disk I 99, gear I 96 and cap I99 to the idle position on the shaft when the magnet I I9 is not energized. The disk |2I is threaded as at I25 and secured to end II9 of lever M9 is a pad I26 that bears against threads I25 when the clutch is disengaged, thus setting up a braking means for shaft I91. Secured to the shaft I91 is a pinion gear I21 that meshes when the clutch is engaged to a large rack gear I29. The gear I28 meshes with racks I29 and I 39 in machine grooves |3| and I 32 respectively, one at the top and one at the bottom right side of the cradle so that the same are similarly arranged as the racks 96 and 91 on the left side of the cradle. A pin I33 projecting from rack I30 engages in a slot 134 in the lower end of the back sight arm 90. The rack I29 simply acts as a counter balance for rack I30 like rack 86 counterbalances rack 91. Thus, the back sight moves only with the objective when the electro magnet is energized and when the magnet is not energized the back sight remains in whatever position it is placed in, a spring I35 serving to take up the backlash of the arm 90.

A range angle scale I38 marked in degrees is flxed to the left side of the cradle 68 by means of arm I31 and screws I38. The scale I36 extends over the edge of the objective 69. between the objective "and eye piece 8|, and when viewed through the eye piece the graduations are erected and magnified. The position of the athwartship cross line 88 on the reticle 82 of the objective read against the scale gives the angle of the line of sight forward of the vertical or the range angle when set for dropping. The position of the back sight can be read by aligning the cross line of the objective with the back sight and reading the scale from the objective cross line.

An athwartship bubble setting knob shaft I39 (Fig. 3) projects through the casing and has a cone surface I40 machined on its end. A spring I4I holds it clear of the cardan but when a knob I42 is pressed in, the cone surface bears against an oppositely disposed cone surface I43 on the cardan so that when the knob I42 is rotated it will exert a torque on the cardan tending to tilt the cardan about the cardan axis in a direction depending u on which way the knob I42 is turned. Applying torque to the cardan about the cardan axis causes the gyro to precess in a direction at right angles to the torque. In this case the gyro and the cradle will tilt together about their respective axes. The direction of spin of the gyro is such that the athwartship bubble 5| moves in the same direction as the top of the bubble setting knob I42. The fore and aft bubble or level 50 is set by applying torque to the gyro case about the gyro case axis, thus producing precession of the gyro in a direction that will tilt the cardan about the cardan axis. This torque is applied by pressing in on a button I44 (Fig. 4) which has a shaft I45 bearing against a spring I46 that presses against the contact surface on the gyro case. The spring I46 is secured by studs I41 to the cardan 30. A spring 340 holds button I44 and shaft I45 clear of spring I46.

Suitably placed on the upper unit 2I of the casing are gyro inspection window I48 and cradle and sight inspection window I49 and in the under side of unit 22 is an objective window I50.

The end 25 is provided with a cylindrical projection I5I in which is rotatably mounted by set screws I52 a shaft I53. Keyed to shaft I53 is bevelled gear I54 having a drum I55 for operating the cable 9|, and a stop I56. An operating knob I51 fits over the outside of the projection I5I and turns on it. The knob I51 is held in place by a key I58 (Figs 4 and 1'1) that has the retaining portion I59 positioned in groove I50 of the knob I51. The key is pivoted by screw I6I and is held against the knob I51 by coil spring I62 having one end secured to arm I63 of the key and the other end to spring II5. A bevelled gear I64 fastened by screws I65 to the plane inner side of knob I51 meshes with the gear I54 on the shaft I53. Thus, the operating knob I51 will wind up or ease off the cable 9I on the drum I55 thereby moving mount 19 with objective 69 to the desired angle. The end of the cable 9i is secured to the drum I55 by set screw I66, and the stop I56 limits the number of turns that can be given the knob I51, thus preventing the breaking of cable III by winding the same on the drum I55. The cable 9| enters the casing 20 through the center of the cardan gudgeon 32 and is guided to the drum 92 by means of pulleys I61 suitably placed on the cardan 30.

Positioned near the sight casing 20 and connected by wires I68 is a clock I69 (see Figs. 10- 12). The clock I69 comprises a reed I10, secured to a, terminal block I1I by screws I12, vibrating between an energizing coil I13 and a de-energizing coil I14 fixed to base I15 of the clock by studs I16. The circuit through coil I13 includes a resilient conducting element I13 that touches a suitable breaker point I13a on reed I10 when the reed is stationary and so maintains this part of the circuit closed. When current flows through coil I13 the reed is drawn toward the coil and the circuit through this coil is broken, but a point I14a on the reed touches contact element I14' and closes the circuit through coil I14 which then draws the reed .toward the last mentioned coil. The length of the reed I10 is such that it will vibrate at a predetermined rate per second, thus providing the means for time keeping. A motor coil I11 secured to base I15 is energized once every vibration of the reed I10 which causes a ratchet bar I19 that is pivoted at I19 to oscillate the same number of times per second. The oscillation of bar I19, acting through a feed ratchet I80, which is held in operative position by spring I8I, causes a ratchet wheel I82 keyed to a shaft I83 to turn one tooth each oscillation of the bar. A drive pinion I84 on top of wheel I82 meshes with a larger gear I85 keyed on a main shaft I86 rotatably mounted in a standard I81 secured by studs I88 to the base I15. The gear I85 is thus turned at a predetermined set rate. A fibre timing disk I89 turns with gear I85 by friction caused through pads I90 on the under side of disk I89 and spring I9I placed in a setting knob I92 bearing against the top of disk I89. The disk I89 may be moved independently of the gear I85 by the knob I92. The timing disk I89 has cut into its periphery a stop notch I93. A pointer I94 secured by stud I95 to the disk I89 and also to the setting knob I92 turns with the disk I89 and indicates on an altitude scale I96'the position of notch I93. The pointer I94 is pointing to zero onscale I96 when a contact I91 that is secured by screws I12 to block "I is just dropped down into the notch I93. A relay coil I98 secured to an arm I99 of standard I81, when energized pulls an armature 200 and closes contact 20I against contact I91 provided contact I91 is any place on disk I89 except in notch I93. Armature 200 is pivoted to frame I99 by pin 203. The armature 200' is pulled away from coil I98 when not energized by a spring 204 held by pin 205 secured to the standard I81. When contact I91 is in the notch I93 the contact between I91 and 20I because of the distance between the two, is broken, even though relay coil I98 is energized. In like manner the ratchet bar I19 is held away from coil I11 by spring I18 held by pin 206 secured to standard I81.

A different clock dial or altitude scale I96 is necessary for each type of bomb, depending particularly upon the weight of the bomb to be dropped. All difficulties are overcome by using on the sight a series of calibrated clock scales which can be made as necessary. The scales may be readily shifted and replaced whenever the type of bomb is changed.

The clock is started in operation by closing main switch 4I8, shown in Figure 20, thus supplying current to coils I13 and I14, which sets the reed I10 into vibration, but the other mechanisms remain stationary. The clock is set for the time corresponding to the altitude. When ready to start the timing operation, the contact ring II 4 on the bomb sight is pressed which closes the timing switch and energizes the relay coil I98. The relay coil I98 pulls contact 20I against contact I91 which closes the circuit through 0011 H and engages the back sight clutch, thus causing the back sight to be driven through rack I 32. gear I28 and the other gears that connect the rack, through the back sight clutch, to shaft 93 and cable drum 92, which drum is rotated at a rate proportional to the ground speed. As above set forth, the back sight clutch is released at the end of the timing interval and hence the back sight stops at a position determined by its rate of motion and the du-, ration thereof. The rate of movement of the back sight is a function of the ground speed of the craft, and since the two arguments of the dropping angle are the time of fall (altitude) and the ground speed of the craft, the back sight will, when positioned in the manner set forth, indicate the correct dropping angle. Contacts I91 and I complete another circuit to the relay coil I98 so that this coil remains energized even though the circuit is broken at the timing switch after the momentary touch given the contact ring II4. Contacts I91 and 20I also complete one leg of the circuit to motor coil I11. The other leg is completed by reed contact I10 once every vibration of the reed. A touch on contact ring I I4 has thus hooked up the-back sight 10 to the objective 69 and started the clock pointer I94 turning around its zero position. When the timing disk I89 rotates to zero seconds, contact I91 drops into notch I93 breaking the circuit to the motor coil I11, relay coil I99 and to the back sight clutch coil Or electromagnet I I 0. The back sight 10 then remains in whatever position it is even though the movement of objective 69 continues.

To re-set the objective 69 the clock pointer I94 should be in the zero position. Contact ring H4 is held in while the operating knob I51 is turned in such a direction as to move the back sight 10 toward its vertical position. A stop 3l2 (Fig. 7) 0n clutch disk I2I will bear against a pivoted pointer 3I3 that will indicate on a stationary pointer 3I4 secured to the cradle by studs 3I5 the vertical position of the back'sight 10.

A terminal box 3I6 with terminals 3| 1 for all outside electrical connections for the bomb sight is provided as an integral part of the end 25. The electromagnet III] is energized when contact ring I I4 is pressed against contact pin 3 I8 that in turn comes in contact with terminal 3I9 in the terminal box 3I6. Suitable wires 320 connect terminal 3I9 to a suitable terminal such as 3 for the magnet II 0.

One of the pulleys I61 is positioned on the carden 30 by means of an arm 32I pivoted by a set screw 322. A spring disposed around screw 322 is engaged therewith and with arm 32I and is under torsional stress in a direction to tend to impart to arm 32I a clockwise rotation about pivot 322 until stopped by pin 324 so that when there is slack in the cable 9| the contacts 325 and 326 will be separated to break the circuit through the coil I I0 and release the back sight clutch to prevent the back sight from getting out of proper relation to the objective. The cable 9| will normally be kept taut by the pull of spring I04 which tends to move objective 69 to a position away from the vertical. When the cable 9| is wound tight between the drums 92 and I55 the force on the pulley I61 will pull arm 32I back until the circuit is again closed through contacts 325 and 326.

A pilot director and azimuth stabilizer for the sight are shown on top of and contained in a casing 201 below the bomb sight casing 20. The casing 201 (see Figs. 13 and 15) has a top or cover plate 208 secured thereto by screws 209, inspection plates 2| 0 and 2I I, a cover plate 2I2 for a servo motor 2 I3 secured to the side thereof, and a bolting face 2 I4 for suitably securing the unit.

A cardan 2I5 is positioned by gudgeons 2I8 that turn in ball bearings 2I1 fitted into the top and bottom of the casing 201. The gudgeons 2I5 are constructed longer than necessary for bearing surfaces in order to fit an electromagnet clutch 2 I8 on the top gudgeon shaft. The clutch 2I8, as shown in the drawings, is fitted on the top gudgeon, while the bottom gudgeon is covered by a protective cap 2I9. In the actual use or construction of the unit, if desired, the protective cap 2 I9 may be shifted to the upper gudgeonand the clutch 2| 8 to the lower gudgeon.

Fitted into cardan 2l5 at right angles to the gudgeons 2I6 are ball bearings 220 in which fit pins 22I for mounting a gyro in casing 222 to stabilize the sight casing in azimuth. The gyro tilts in the cardan about a horizontal axis. The gyro 222 is of the same design and construction as gyro 33 used and described in the bomb sight casing 20. Caps 223 secured to the casing 222 for the gyro bearings and shaft, not shown, are extended to form tilting stops 224 to limit the tilt of the gyro to a predetermined number of degrees each side of the horizontal by being brought up to the inner sides of the casing 201. Fixed to the shoulders 225 on the cardan 2I5 by screws 226 is a circular gear 221, upon which the servomotor 2I3 exerts its torque. The cardan 2I5 also carries adjacent the top gudgeon, slip rings 228 (Fig. 19) for distributing electric current to the various parts of the instrument. By use of the rings 228 and the brushes 229 that bear against the rings 228, the cardan stabilization is not aifected by whatever course the craft takes or by any position the cardan happens to be in when the stabilizer is started. The cardan also has fastened thereto insulated control sectors 230 and 23I, separated by a neutral gap 232 (Fig. 13), and riding on the sectors is the brush 233 which is secured to arms 234 on the gyro casing by screws 235.

The electromagnet clutch 2I8 consists of a disk 236 keyed on the gudgeon 2I6 by nut 230 threaded on the end of the gudgeon 2I6, and an electromagnet 239 having a non-magnetic bushing or friction plug 240 adapted to bear against disk 236. The magnet 239 houses an energizing coil 2 controlled by a switch 242. A lever 243 (Fig. 19) is secured to the clutch by studs 244, and a rod 245 connects the clutch lever 243 to a clamp lever 246 that is secured to a sleeve 241 (Fig.

6) for the sight fork 29, thus establishing parallel motion between the clutch 2| 8 and the fork 28. When the switch 242 is closed, the magnet is coupled to cardan 2I5 and the sight fork 20 is directly stabilized in azimuth by the gyro which maintains its plane of rotation and holds the line of sight through objective 69 constant even though the craft yaws or changes course.

An armature shaft 248 (Fig. 19) of the servomediate gear 26!.

motor has a pinion 249 on one end thereof, which drives throughintermediate gear 250 and pinion 25! a clutch gear 252 which in turn drives a similar clutch gear 253 in a reverse direction at the same speed. The gears 252 and 253 turn constantly in opposite directions on shafts 254 and 255 respectively when current is on the instrument. The gears 252 and 253 have inserted in their upper surfaces a number of friction plugs 256. Fixed on the shafts 254 and 255 upon which the clutch gears 252 and 253 turn idly, are clutch disks 251 and 258 which have smooth slipping surfaces on their under sides, and each of said shafts 254 and 255 have keyed thereto pinions 259 and 260 which mesh with an inter- The gear 26l is keyed on one end of a shaft 262 that has on its other end a pinion 263 which in turn meshes with gear 221 secured to the cardan.

The clutch disks 251 and 258 are kept out of contact with gears 252 and 253 by flat springs 264 pushing up against the lower ends of shafts 254 and 255 which end below the bearing plates 266 that hold them. The clutch disks 251 and 258 are forced down against the plugs 256 of the gears 252 and 253 respectively by armatures 261 working in solenoids 268 which are energized by the tilting control sectors 230 and 21 on the cardan 2 l5 and the brush 233 on the gyro casing 222.

When the gyro 222 in the cardan 2l5 tilts in space about the gyro case tilting axis, the brush 233 of the gyro case 222 carries current to one or the other of the sectors 230 or 23! on the cardan, and thereby energizes one of the solenoids 268 for the servomotor clutch disks 251 and 258 and clutch gears 252 and 253, thereby applying a torque on the cardan 2l5 which precesses the gyro back to the neutral gap position.

The pilot director bracket unit has a sleeve bracket 269 secured to either the aircraft or pilot director casing, as desired. This bracket 269 has inserted sleeve 241 which is connected to the cardan 2l5 through the magnet clutch 2|8, rod 245 and levers 243 and 246, mounted, in a vertical position. A fork shaft 210 holding bomb sight fork 28 by means of grooved arms 2' and clips 212 extends into the sleeve 241 which provides journal and thrust bearings for the shaft 210. The shaft 210 is free to turn in the sleeve 241. Integral with sleeve 241 is a bracket 213 to which is secured by studs 214 (Fig. 18) a helical gear sector 215 that is also stabilized for the vertical axis.

A worm gear housing 218 is afiixed to the arm 2H and mounted therein is the worm gear 211 that is an integral part of a training shaft 218 extending from the housing 216. Worm gear 211 meshes with the sector gear 215. A training knob 219 is keyed to the free end of shaft 218. The gears 215 and 211 are such that one turn of the knob displaces the sight fork 28 a predetermined amount. Thus, for quick training or for target finding the electromagnet clutch 218 is released, making the sight fork 28 free to rotate within plus or minus 45 degrees from the fore and aft center-line of the aircraft. The helical gear sector 215 is toothed for 120 degrees so that after rough training, there is ample space for great changes of line of sight in space. Although we have used certain definite values in degrees, it is to be understood that these values may be varied as desired.

A second tooth or brush gear sector 280 rides on a bushing 28f that is an integral part of the sleeve 241. Sliding axially along the training shaft 218 (Fig. 18) and keyed to it by pin 282 extending into slot 2831s a gear shift sleeve 284. On

the left end of this sleeve, a gear 285 is fixed and on the other end is a knob 286 for moving the sleeve to-engage gear 285 with, and disengage it from, gear 29!. Springs 281 fixed to knob 219 and working in corresponding notches 288 in the sleeve 284 keep the sleeve in the selected position.

Mounted in brackets 289 above the gear housing 216 is a horizontal shaft 290 that has on one end thereof gear 29! which is adapted to mesh with gear 285 when the sleeve 284 is moved to its innermost position. Keyed on the other end of the shaft 290 is bevelled pinion 292 that drives a smali'vertical shaft 293, rotatably mounted in housing 294, by means of bevelled gear 295 on the end thereof. On the lower end of shaft 293 is keyed gear 296 that meshes with the brush sector gear 280. Fixed to bracket 289 is a star-shaped spring 291 which presses against the flat surface of the gear 29f on the end of the horizontal shaft 290. The tension on the spring 291 is suflicient to prevent gear 29l from turning when the training knob 219 is turned, except when gears 285 and 29l are engaged. The brush gear sector 280 carries a brush arm 298 to which is fixed a brush 299. The brush 299 rides over a commutator bar 300 which is fixed to the stabilizing unit bracket 269 and therefore to the aircraft. The commutatorbar 300 consists of a number of segments on each side of a neutral gap. The brush moves over an arc of 4X 6-inch radius for which /ia.1tinch motion=1 Although certain definite dimensions have been stated for the brush movement, We desire it to be understood that these dimensions may be changed as desired. The segments are connected to parts of a resistance coil 30l which in turn is in circuit with a double reading volt meter 302. With the brush 299 on the neutral gap, the needle of the volt meter 302 will be in the central position, indicating straight flight to the pilot. With the brush 299 on any other segment of bar 300, the volt meter will read to the right or left by an amount depending upon which segment the brush 299 is resting and indicating to the pilot the direction and proportionate amount of the change of course. Owing to the non-yielding coupling of the brush gear 280 to the training shaft 218 when the gear shift 284 is in the engaged position, it is necessary to provide the commutator with extensions 303. While the brush rides over these extensions 303. the pilots instrument will show maximum angles. A brush adjusting knob 304 which is attached to the brush arm 298 permits hand shifting of the brush 299 and adjustment to the neutral gap When the gear shift 284 is disengaged. When the gear shift is engaged, knob 304 cannot be moved.

Rotatably positioned on one arm 21! of fork shaft 210 is shaft 305 that has a knob 306 on one end thereof and pinion 301 on the other end. Pinion 301 meshes with a gear 308 keyed to shaft 309 mounted in the arm 2H, and gear 308 in turn meshes with a pinion 3l0 also keyed on shaft 309. The pinion 3l0 meshes with rack teeth 3| 1 on the fork 28 so that by turning knob 306 the fork 28 may be turned in arm 21! of the fork shaft. Thus, the sight may be kept in a horizontal position at all times regardless of the position of the aircraft to Which the device is attached.

The action of the pilot director mechanism is as follows: When the gear shift sleeve 284 is in the disengaged position turning the training knob 219, turns the training shaft 218 and the worm 211' which is in the worm gear housing 219.

The worm 211 tends to turn the helical Sear sector 215 but this sector being secured to the stabilized sleeve 241 remains fixed in space in the worm gear 211 and housing 218 and fork shaft 219 which are fixed together and hence the bomb sight and the line of sight turn in reference to cardan H5. The brush gear sector 280 is also carried on the stabilized sleeve 241, but by friction only. Ordinarily, turning the training knob 219 which causes the bomb sight fork shaft 210 to turn in reference to the helical gear 215 would cause the gear shift train to turn idly by being rotated about the gear shift or brush sector 280. But the star-shaped spring 291 has sufficient friction to lock the gear 29i on the end of the horizontal shaft 290 and the rest of the gear train so that the brush gear sector 289 slips on its hub bearing and the brush gear sector 280 is turned on the sleeve 241 together with the bomb sight fork shaft 219. The brush 299 is thus displaced the same amount as the line of sight and the director is set to have a one to one correction ratio.

When the gear shift sleeve 284 is in the engaged position turning the training knob 219, moves the fork shaft 219, the fork 28, bomb sight and line of sight as before. It also turns the gear shift train, the gear 2! on horizontal shaft 290 slipping against the friction of the spring 291. The gear shift train turns the brush gear sector 280 on the stabilized sleeve 241 against the friction on its hub bearing. The gear ratio and the gear shift train is such that the brush 299 is displaced 6.2 times as much as the line of sight and therefore, there is a 6.2 overcorrection which brings the craft more quickly upon a collision course.

When the gear shift sleeve 284 is in either position and the aircraft turning but the knob 219 remaining stationary, the helical gear sector 215, fork 28, bomb sight, line of sight, brush gear sector 28!! and brush 299 are all on the stabilized sleeve 241 and remain fixed in space. The commutator bar 300 being fixed to the aircraft moves with reference to the brush 299 and the pilot receives an indication on the volt meter 302 to return to his course.

In the practical use of our improved device the bomb sight is mounted on the pilot director bracket unit that may be aflixed separately on the aircraft at any place suitable for a bomber or it may be mounted on the stabilizing or pilot director casing. The pilot director may be secured to the aircraft in any convenient position where the clutch lever 243 can be coupled by connecting rod 245 to the bracket unit.

About ten minutes before starting a. bombing run, it is best to turmon the master switch 321 shown in Figure 20. This switch 321 is so designed that the first snap is on contact 328 that delivers power to the stabilizer unit. The stabilizer is permitted to run a minute or two, then the switch snapped twice to contact 329 which delivers current to both stabilizer and bomb sight as well as all other accessories. The second contact 330 of the switch 321 delivers power to the bomb sight alone and need not be used except for test purposes.

Before setting the sight on the target the backsight should be at zero, which is shown when pointer 3i3 connected to the back sight is aligned with stationary pointer 3l4 (Fig. '7) These pointers are in the field of the eye piece 8| when the objective 69 is at its maximum angle with the vertical.

The clock I89 is then set for the altitude at which the bombs are to be released. The indicator switch 33l is then turned on and the sight is swung right and left to inform the pilot that the sight is ready for approach. As soon as the target comes into view, manual directing is done by knob 219 until the target is approximately in the center of the eye piece 8|. The bomb sight gyro 33 is then unlocked by releasing locking knob BI and the bubbles 59 and 5| are leveled exactly by the levelling knob I42 and the button I44. The bomb sight case is then placed in the horizontal position by operating knob 386. The switch 242 is snapped so as to engage clutch H8, and then engage overcorrection sleeve 284 and pilot director, until cross line 81 is on the target.

It is better to allow the vertical cross line 81 to keep off and give fairly large changes in course, than to be continually turning pilot directing knob 219 to keep cross line 81 exactly on the target and, therefore, at intervals of a few seconds turn the pilot directing knob 219 to put the vertical cross line 81 on the target. As soon as the vertical cross line 81 settles fairly steady on the target, disengage the overcorrection sleeve 284 and pilot direct with the one to one gearing. A minute is ample to settle the vertical line 81 on the target after which the target should follow very closely down the vertical cross line 81 as the objective 69 is continuously rotated by means of knob I51, cable 9 i, and the gears associated therewith. The clock setting is then checked with the actual altitude and the gyro levels 58 and 5! are also rechecked. When the target is on the horizontal cross line and the objective 69 is approximately 40 degrees from the vertical, place the cross line 88 just ahead of it and when the target comes again exactly on cross line 88, press the timing ring H4, rotating the objective to keep the cross line 88 on the target until the clock stops. It is very important that cross line 88 is on the target when the clock is started and also when the clock stops to insure that the backsight will be driven proportionately to the ground speed during the timing interval. The operating knob I51 is then turned to keep cross line 88 on the target until the cross line 88 is aligned with the back-sight pointer 10, at which point the bomb is released. The time interval from the end of timing to the release of the bomb is usually of suihcient length to permit of slight correction of pilot direction; one to one ratio should always be used in this case and the operator should use discretion in applying it.

Immediately after release, the bomb sight gyro 33 is locked, the back-sight is returned to zero, and all the electrical switch connections are shut off, thus completing the bomb run.

What we claim is:

1. In combination, a bomb sight having an. optical system therein, means stabilizing at least a portion of the said optical system for the fore and aft position and for the athwartship position, a pilot director and pilot director bracket, means connecting said director and bracket to said sight whereby said sight is stabilized about the vertical axis.

2. In combination with an aircraft, a bomb sight, a pilot director, a pilot director bracket, overcorrection means carried thereby to bring the aircraft more quickly upon a collision course in sighting a target, and means connecting said director and bracket to said sight.

3. In combination with an aircraft, a, bomb sight having an optical system therein, means stabilizing said sight for the fore and aft position, and for the athwartship position, a pilot director, a pilot director bracket having overcorrection means thereon for indicating the correct course of the aircraft in sighting a target, and means connecting said director and bracket to said sight whereby said sight is stabilized about the vertical axis.

4. In combination with an aircraft, a bomb sight, an optical system in said sight comprising a fore-sight and a back-sight, a clock adapted to run for a period corresponding to the time of fall at a set altitude, means controlled by said clock for setting the back-sight at the proper dropping aft position and for the athwartship position, a

pilot director and pilot director bracket, and means connecting said director and bracket to said sight whereby said sight is stabilized about the vertical axis.

5. In combination with an aircraft, a bomb sight, a cradle in said sight, an optical system mounted in said cradle comprising an objective and a back-sight, a clock in which the altitude of the aircraft is set and which is adapted to transmit to the bomb sight the time said backsight will move in the fore and aft direction, means for moving said objective, a clutch means secured to said cradle for moving said back-sight with said objective when the clock is setting said back-sight to the proper dropping angle, means in said sight stabilizing said cradle for the fore and aft position and for the athwartship position, and means connected to said bomb sight stabilizing the same about the vertical axis.

6. In combination with an aircraft, a bomb sight, a cradle in said sight, an optical system mounted in said cradle comprising an objective and a. back-sight, a clock, means controlled by said clock for setting said back-sight to the proper dropping angle,,means for moving said objective, a clutch means secured to said cradle for moving said back-sight with said objective when the clock is setting said back-sight to the dropping angle, means in said sight stabilizing said cradle for the fore and aft position and for the athwartship position, a pilot director, a pilot director bracket, and means connecting said director and bracket to said sight whereby said sight is stabilized about the vertical axis.

7. In combination with an aircraft, a bomb sight having a cardan therein, a cradle positioned in said cardan, an optical system mounted in said cradle, said system comprising an objective, an objective mount, and a back-sight positioned on a portion of said mount, means adapted to move said objective and mount independently of said back-sight, said moving means having counterbalanced racks whereby said cradle is not disturbed from its stabilized position, a clock connected with said sight, means controlled by said clock for setting said back-sight to the correct dropping angle, a clutch means seccured to said cradle for moving said back-sight with said objective when the clock is setting said back-sight, a gyro mounted in said cardan, means connecting said gyro to said cradle for stabiliing the cradle and'means connected to said sight stabilizing the sight about the vertical axis.

8. In combination with an aircraft, a bomb sight, a cardan pivoted in said sight, a cradle mounted in said cardan, means stabilizing said cradle, an objective mount in said cradle, an objective positioned in said mount, a back-sight positioned on said mount, means for moving said objective and mount independent of said backsight, said means having counterbalanced racks, and means for moving said back-sight having counterbalanced racks whereby the movement of said objective and back-sight racks will not disturb the cradle from its stabilized position.

9. In combination with an aircraft, a bomb sight, a cardan pivoted in said sight, a cradle mounted in said cardan, means stabilizing said cradle, an objective mount in said cradle, an objective having a cross line reticule positioned in said mount, a scale reading against said reticule secured to said cradle, a back-sight rotatably positioned on said mount opposite said scale, means moving said mount independent of said back-sight, means for moving said back-sight, and clutch means adapted to engage the moving means for both the objective and back-sight.

10. In combination with an aircraft, a bomb sight having a cardan pivoted therein, an optical system mounted in said cardan, a gyro positioned in said cardan, means connecting said gyro to said optical system for stabilizing the same, a fore and aft level and an athwartship level positioned on said gyro, and means adapted to set said gyro and cradle to a vertical position while the aircraft is flying a straight level course.

11. In combination with an aircraft, a bomb sight having a cardan pivoted therein, a cradle positioned in said cardan, an optical system mounted in said cradle, a gyro positioned in said cardan parallel to said cradle, means connecting said gyro to said cradle for stabilizing the same, a fore and aft level and an athwartship level affixed to said gyro, means for applying torque to the cardan to cause the gyro to precess in a direction at right angles to the torque applied and means for applying torque to the gyro to cause the cardan to tilt about the cardan axis.

12. In combination with an aircraft, a bomb sight, an objective, means movably mounting said objective in said sight, means stabilizing said objective for the fore and aft and the athwartship positions, a back-sight, a scale for reading the position of said objective and back-sight, 8. cable, and means whereby said objective may be moved by said cable.

13. In combination with an aircraft, a bomb sight having an optical system, means whereby a portion of said system may be stabilized for the fore and aft and for the athwartship positions, a back-sight mounted in said optical system, and a clock connected with said back-sight in said bomb sight, said clock comprising a removable face marked with an altitude scale, altitude being an argument of time of fall, a hand adapted to run for a period corresponding to the time of fall at a set altitude, means for operating said hand, and means controlled by said clock for setting said back-sight at the correct dropping angle.

14. In combination with an aircraft, a bomb sight having an optical system, means whereby a portion of said system may be stabilized for the fore and aft and for the athwartship positions, a back-sight mounted in said optical system, and a clock connected with said back-sight in said bomb sight, said clock comprising a removable face marked with an altitude scale, altitude being a function of time of fall, a hand adapted to run for a period corresponding to the time of fall at a set altitude, frequency vibrating means for operating said clock and hand,

and means controlled by said clock for setting said back-sight at the correct dropping angle.

15. In combination with an aircraft, a bomb sight, a pilot director, a pilot director bracket unit for mounting said bomb sight, overcorrection means on said bracket unit for indicating the correct course of the aircraft in sighting a target and means on said bomb sight mounting for keeping the sight in a horizontal position regardless of the position of the aircraft.

16. In combination with an aircraft, a bomb sight having an optical system therein, means whereby a portion of said system may be stabilized for the fore and aft and for the athwartship positions, a pilot director having stabilizing means therein, and means for transmitting motion of said stabilizing means to said sight whereby the sight is stabilized about the vertical axis.

1'7. In combination with an aricraft, a bomb sight, a pilot director and a pilot director bracket unit, said pilot director comprising astabilizing means, and means connecting said pilot director to said bomb sight to stabilize the sight about the vertical axis, means connecting said sight to said pilot director whereby movements of the sight around the vertical axis are transmitted to said director as indications of changes in course, and

, means associated with said sight and said director to move said sight about the vertical axis and cause such movement to be transmitted to the director with increased magnitude.

18. In combination with an aircraft, a bomb sight, a. pilot director comprising means for stabilizing the sight about the vertical axis, means connecting said director to the bomb sight whereby movement of said sight about the vertical axis is transmitted to the pilot director, and a pilot director bracket unit having overcorrection mechanism for moving said sight about the vertical axis including means thereon for augmenting the pilot director indication of such movement.

19. In combination with an aircraft, a bomb sight, an objective, means movably mounting said objective in said sight, means stabilizing said objective for the fore and aft and for the athwartship positions, a pilot director, means for stabilization about the vertical axis, means connecting said director to said bomb sight whereby said sight will be stabilized about the vertical axis and a pilot director bracket unit having overcorrection means thereon of indicating the correct course of the aircraft in sighting a target.

20. In combination with an aircraft, a pilot director bracket unit, a bomb sight mounted on said unit, a pilot director comprising a gyro sta- .bilized about the vertical axis, and means connecting said director to said bracket unit whereby said gyro stabilizes the sight about the vertical axis.

21. In combination with an aircraft, a pilot director bracket unit, a bomb sight mounted on said unit, an objective positioned in said sight, means stabilizing said objective for the fore and aft and for the athwartship positions, a pilot director comprising a gyro stabilized about the vertical axis, and means connecting said director to said bracket unit whereby the gyro in the director stabilizes the sight about the vertical axis.

22. In combination with an aircraft, a bomb sight, a pilot director bracket unit in which said sight is mounted, a pilot director, a cardan, gudgeons positioning said cardan in the director, a gyro mounted in said cardan, means for causing precession of said gyro, means on said cardan 16 and gyro controlling the said precession causing means, and means connecting said director to said bracket unit whereby the gyro stabilizes the sight about the vertical axis.

23. In combination with an aircraft, a pilot director bracket unit, a bomb sight mounted on said bracket unit, a. pilot director, a cardan, two gudgeons positioning said cardan in the director, a gyro mounted in said cardan, a servomotor, means connecting said cardan to said servomotor. whereby said servomotor can precess said gyro, means responsive to relative tilting movement between the gyro and the cardan to control the application of the precessing effort and means connecting said director to said bracket unit whereby to stabilize the sight about the vertical axis.

24. In combination with an aircraft, a pilot director bracket unit having a lever extending therefrom, a bomb sight mounted on said bracket unit, a pilot director, a cardan, two gudgeons positioning said cardan in the director, a gyro mounted in said cardan, a. servomotor, means connecting said cardan to said servomotor whereby said servomotor can precess said gyro, means responsive to relative tilting movement between the gyro and the cardan to control the precessing force, a clutch having a clutch lever attached thereto on one of said gudgeons, an energizing coil in said clutch adapted to engage members of said clutch and a rod connecting the clutchlever to said bracket lever whereby the .cardan is linked to said sight to stabilize the sight about the vertical axis.

25. In combination with an aircraft, a pilot director bracket unit having a lever extending therefrom, a bomb sight mounted on said bracket unit, an optical system positioned in said sight, means stabilizing a portion of said system for the fore and aft and for the athwartship positions, a pilot director, a cardan, two gudgeons positioning said cardan in the director, a gyro mounted in said cardan, a servomotor, means connecting said cardan to said servomotor whereby said servomotor can precess said gyro, means responsive to relative tilting movement between the gyro and the cardan to control the precessing force, a clutch having a clutch lever attached thereto on one of said gudgeons, an energizing coil in said clutch adapted to engage members of said clutch and a rod connecting the clutch lever to said bracket lever whereby the cardan is linked to said sight to stabilize the sight about the vertical axis.

26. In combination with an aircraft, a pilot director bracket unit having overcorrection means thereon for bringing the aircraft quickly on a collision course in sighting a target, a bomb sight mounted on said bracket unit, an optical system positioned in and on said sight, means stabilizing a portion of said system in said sight for the fore and aft and for the athwartship positions, a pilot director comprising a gyro for stabilization about the vertical axis, means for precessing said gyro to a predetermined relative position, means controlling said precessing means and means linking said gyro to said bracket unit whereby the sight is stabilized about the vertical axis.

27. In combination with an aircraft, a pilot director bracket unit having overcorrection means thereon for bringing the aircraft quickly on a fore and aft and for the athwartship positions, an objective mounted in the cradle, a back-sight, means for moving said objective, a clock adapted to run for a period corresponding to the time of fall at a set altitude, means controlled by said clock for setting the back-sight at the proper dropping angle, a pilot director comprising a gyro for stabilization about the vertical axis, means for precessing the gyro to a predetermined relative position, means controlled by the movement of said gyro for regulating said precessing means, and means linking the gyro to said bracket unit whereby the sight is stabilized about the vertical axis.

28. In combination with an aircraft, a bomb 7 sight having an objective therein, means stabilizing said objective for the fore and aft and for the athwartship positions, a double reading voltmeter, a pilot director bracket unit in which said bomb sight is mounted, said unit comprising a sleeve bracket secured to the aircraft, a sleeve movably positioned in said bracket, a fork shaft rotatably mounted in said sleeve, a segmented commutator secured to the sleeve bracket and electrically connected with said voltmeter, a brush adapted to ride over said commutator thereby registering movement on said voltmeter, training means for moving said fork and brush on said commutator thereby indicating on the voltmeter the correct course to be taken in sighting a target, and a pilot director stabilized about the vertical axis, and means connecting said director to said sleeve to stabilize the bomb sight about the vertical axis.

29. In combination with an aircraft, a bomb sight having an objective therein, means stabilizing said objective for the fore and aft and for the athwartship positions, a double reading voltmeter, a ilot director unit in which said bomb sight is mounted, said unit comprising a sleeve bracket secured to the aircraft, a sleeve movably positioned in said bracket, a fork shaft rotatably mounted in said sleeve, a segmented com mutator secured to the sleeve bracket and electrlcally connected with said voltmeter, a brush gear sector on said sleeve, a brush secured to said sector and adapted to ride on said commutator, thereby registering movement on said voltmeter, a training shaft having gears meshing therewith for moving said brush at a one to one ratio, a

shift sleeve on said shaft, and gears meshing with said sleeve when in the engaged position whereby said brush is displaced an overcorrection ratio, and a pilot director stabilized about the vertical axis having means connecting said director to said sleeve to stabilize the bomb sight about the vertical axis.

30. In combination, a bomb sight having an optical system, means to stabilize at least a portion of said optical system about the horizontal axis, a pilot director, and means connecting said sight and said pilot director whereby the pilot director is actuated to indicate a change in course of said-craft when such occurs after a line of sight has been established through said sight.

31. In combination, a bomb sight having an optical system, means to stabilize at least a portion of said optical system about the horizontal axis, a pilot director, and means connecting said sight and said pilot director whereby the pilot director will be caused to indicate a course to be followed in conformity with a line of sight through said bomb sight.

32. The combination of a bomb sight unit having means to stabilize the optics only and a pilot director unit that includes means for stabilizing the sight unit as a whole about one axis.

33. The combination of a bomb sight unit having means to stabilize the optics thereof and a pilot director unit that includes means for stabilizing the sight unit as a whole.

CARL L. NORDEN. THEODORE H. BARTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,279,471 Sperry Sept. 17, 1918 1,783,769 Bates Dec. 2. 1930 1,688,599 Sperry Oct. 23, 1928 1,468,712 Ford Sept. 25, 1923 1,446,280 Titterington Feb. 20, 1923 FOREIGN PATENTS Number Country Date 594,563 France June 27, 1925 270,349 Germany Feb. 13, 1914 

